1. Field of Invention
This invention relates to electrical circuit and systems. More specifically, the present invention relates to transmission lines.
2. Description of the Related Art
In electrical circuit technology the advantages of a shielded signal path are well known. In transmission lines shielded conductors are widely used. The coaxial cable is an example of an improved transmission line having well known advantages stemming from its symmetry properties.
In microcircuits it has been long desired to achieve the advantages of shielded transmission lines, but planar fabrication techniques have not been acceptable to achieve this until now. The closest prior art, are the well-known on-chip stripline and the microstrip structures. These transmission line structures are not typically isolated well from surrounding electromagnetic fields. Improvements in isolation have been achieved through physical separation from neighboring circuit elements and signal paths. However, this approach takes up valuable surface area on the chip.
There is a need for an isolated, shielded conductor used on-chip without consuming an inordinate amount of space. More specifically, there is a need for an isolated, shielded conductor used on-chip at radio frequencies (RF).